Synchronous flow control in wormhole routed optical networks

In this paper, we propose a synchronous flow control mechanism in wormhole routed optical networks. It is expected that the benefit of shorter routing delay and smaller buffer size requirement in wormhole routing will be significant in optical networks. Different from the traditional bi-directional asynchronous back-pressure flow control, the flow control is modified to be unidirectional and synchronous. The size of synchronized control slot does not depend on the routing path length and the number of bits is a constant which is equal to the total number of virtual channels and nodes. The proposed flow control takes advantage of the restricted order of accessing channels in deadlock-free routing to broadcast their control information in a corresponding restricted order. Furthermore, in order to reduce the buffer size to only one unit, the virtual channels which share the same physical channel must be able to simultaneously transmit data. The low channel utilization induced by such mechanism is overcome by our modified source routing. In summary, this paper introduces a flow control mechanism which easily incorporates the benefit of wormhole routing into the limited-resource optical networks.